Blowout preventers used on drilling rigs for the construction of wellbores must routinely be internally pressure tested to ensure optimal operational functionality and to demonstrate integrity. Blowout preventers are commonly designed to prevent escape of fluids and gasses during the drilling of a well. In some jurisdictions, blowout preventers are tested every 10-14 days and at the transition of an operation. Water is the most common test fluid used for such pressure testing. Such pressure testing procedures are usually conducted manually, i.e. a test pump is connected to the vessel to be pressure tested, and the test pump is operated manually while volumes pumped vs. resultant pressures are manually observed. The length of time required to perform a pressure test on a blowout preventer on a rig can be unpredictable, and, in many cases, can take many hours or even days to perform. The requirement to perform such pressure tests is an interruption that delays the drilling process and adds to the overall cost of constructing the well. When conducting an internal pressure test such as when using water as the test medium, it is desired for the apparatus undergoing test to first be entirely prefilled with water.